What is CVE-2026-21868?

CVE-2026-21868 is a high-severity vulnerability in Flagforge, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-01-08.

How severe is CVE-2026-21868?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Flagforge

CVE-2026-21868

Flag Forge is a Capture The Flag (CTF) platform. Versions 2.3.2 and below have a Regular Expression Denial of Service (ReDoS) vulnerability in the user profile API endpoint (/api/user/[username]). The application constructs a regular expre…

Vulnerability class: ReDoS (Regular Expression Denial of Service)

EPSS: 0.003 (18.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Flagforge
Flagforgectf Flagforge — versions < 2.3.3

Weakness classification (CWE)

CWE-1333 — Inefficient Regular Expression Complexity

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)

Frequently asked questions

What is CVE-2026-21868?: CVE-2026-21868 is a high-severity vulnerability in Flagforge, classified under Inefficient Regular Expression Complexity. CVSS score: 7.5/10. Published 2026-01-08.
How severe is CVE-2026-21868?: High severity. CVSS v3 base score is 7.5 out of 10.